Python-liquid

- Only clear environment-wide template cache if the cache is not `None`. Python Liquid
version 1.9.0 changed `liquid.Environment.cache` to be an `Optional[Mapping]`.
- Handle depreciation of `flask.signals_available`.
- Require Flask version 2.

**Features**

- New general purpose argument list parser. Parse Liquid expressions containing any number of named or keyword arguments, with a choice of key/value separator. See `src/expressions/arguments/parse.ts`.
- New inline comment tag `{% .. %}`. See [Shopify Liquid PR 1498](https://github.com/Shopify/liquid/pull/1498).

**Fixes**

- Fixed a bug with the `assign` tag where it would incorrectly throw a `LiquidSyntaxError` when parts of its expression were split over multiple lines.
- Fixed a bug with the `where` filter. It is now consistent with the reference implementation when given `nil` or `Undefined` as its second argument.
- Fixed a bug with the `sort` filter. It now raises a `LiquidTypeError` at render time if the items to be sorted are incompatible. The reference implementation raises an equivalent `Liquid::ArgumentError` in this situation.

**Docs**

- New example Jekyll-style `include` tag.

- Fixed a bug where double pipe characters (`||`) in a filtered expression would cause an `IndexError`. A `LiquidSyntaxError` is now raised in such cases, including the line number of the offending error.
- Changed `Environment.fromString` to catch unexpected parsing errors. A Liquid `Error` will now be raised with a message of "unexpected liquid parsing error" and its `__cause__` set to the offending exception.

- Fixed a bug where the `where` filter would incorrectly ignore an explicit `false` given as the target value. See 51.

- Prioritise object properties and keys named `size`, `first` and `last` over the special built-in properties of the same names. See 46.
- Fixed a bug with the `uniq` filter. It no longer raises an exception when given a key argument and a sequence containing objects that don't have that key/property. See 47.
- The `strip_html` filter now removes `style` and `script` tag blocks in their entirety, including everything in between. See 45.
- Added `remove_last` and `replace_last` filters.

- Lazy `forloop` helper variables. Don't calculate `index`, `rindex` etc. unless accessed.
- Implemented `forloop.name`, as per the reference implementation. `forloop.name` is the concatenation of the loop variable identifier and the target iterable identifier, or a string representation of a range literal, separated by a hyphen.
- Fixed a bug with the `divided_by` filter. Given a float value and integer argument, it was incorrectly doing integer division.
- Simplified `tablerowloop` and `tablerow` HTML generation.